Drive High Current BLDC Motors in Consumer and Industrial Applications

March 14, 2017

Allegro MicroSystems, LLC announces a new three-phase brushless BLDC motor controller for use with N-channel external power MOSFETs. Allegro’s AMT49413 incorporates much of the circuitry required to design a cost-effective, three-phase motor drive system with maximum supply voltages up to 50 V. This new device is targeted at high current BLDC motor applications for speed, position, or torque control requirements. It has been designed for battery powered power tools, lawn and garden equipment and factory automation, pumps, fans, blowers and appliance applications within the consumer and industrial markets.

The AMT49413 provides functionality over a wide input supply range. A unique charge pump regulator provides adequate (>10 V) gate drive for battery voltages down to 7 V, and allows the device to operate with a reduced gate drive at supply voltages down to 5.5 V. A bootstrap capacitor is used to provide the above-battery supply voltage required for N-channel MOSFETs. An internal charge pump for the high-side drive allows for DC (100% duty cycle) operation.

Internal fixed-frequency PWM current control circuitry can be used to regulate the maximum load current. The peak load current limit is set by the selection of an input reference voltage and external sensing resistor. The PWM frequency is set by a user-selected external RC timing network. For added flexibility, the PWM input can be used to provide speed and torque control, allowing the internal current control circuit to set the maximum current limit. Efficiency is enhanced by using synchronous rectification.

A full suite of protection features is provided including MOSFET shoot-through, undervoltage, overvoltage, HALL logic fault, low motor current and short to ground, supply and across motor winding. The dead time can be set by a single external resistor.

The AMT49413 is supplied in a 48-pin QFN with exposed thermal pad. This is a small footprint (7mm x 7mm) power package, that is lead (Pb) free, with 100% matte-tin leadframe plating.